Uniqueness constraints on vertical fact types are horizontal

[hidders]

The uniqueness constraints on vertical fact types seem to be drawn horizontally. For example, the following code:

\documentclass{standalone} 

\usepackage{tikz}
\usetikzlibrary{positioning} % ...positioning nodes
\usepackage{tkz-orm}  % the ORM2 package


\begin{document}
\begin{tikzpicture}
  \entity (A) at (0, 0) {A};
  \node (R) [vroles=2, unique=1-2, below=1cm of A, label=above:{R}] {};
  \plays (A) -- (R.two east);
  \entity (B) [below=1 cm of R] {B};
  \plays (B) -- (R.one west);
\end{tikzpicture}
\end{document}

Gives:

Also the positioning of the vertical fact types seems a bit odd here, but that is another issue.